设z=x-y/x+y,求解dz

完全不懂,烦请给出正确答案,谢谢

第1个回答  2015-10-12
az/ax=[(x+y)-(x-y)]/(x+y)²
=2y/(x+y)²
az/ay=[-(x+y)-(x-y)]/(x+y)²
=-2x/(x+y)²
dz=2y/(x+y)² dx-2x/(x+y)²dy本回答被提问者和网友采纳